The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

Duncan, K. J.; Kondapally, R.; Brown, M. J. I.; Bonato, M.; Best, P. N.; Röttgering, H. J. A.; Bondì, M.; Bowler, R. A. A.; Cochrane, R. K.; Gürkan, G.; Hardcastle, M. J.; Jarvis, Matt J.; Kunert-Bajraszewska, M.; Leslie, S. K.; Małek, K.; Morabito, L. K.; O’Sullivan, S. P.; Prandoni, I.; Sabater, J.; Shimwell, T. W.; Smith, D. J. B.; Wang, L.; Wołowska, A.; Tasse, C.

doi:10.1051/0004-6361/202038809

Cited by 67 publications

(83 citation statements)

References 98 publications

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“…About a quarter of the final area of DR2 has complete optical identifications as the end product of these processes at the time of writing, and the overall optical identification fraction is 87%, with 97.7% of these having optical IDs from the likelihood ratio process, 0.7% from the ridge line code and 1.5% from visual inspection in Radio Galaxy Zoo or the other manual processes; thus it seems likely that the optical ID fraction in DR2, with the improved optical depth of the Legacy survey, will be significantly higher than the 73% achieved using Pan-STARRS with LoTSS-DR1. A final value-added catalogue for the DR2 radio sources, with photometry and estimated photometric redshifts, will be produced in the manner described by Kondapally et al (2021) and Duncan et al (2021), and we hope to be able to release such a catalogue publicly by the end of 2022. A detailed description of the process will be given by Hardcastle et al (in prep).…”

Section: Value-added Cataloguementioning

confidence: 99%

The LOFAR Two-metre Sky Survey

Shimwell

Hardcastle

Tasse

et al. 2022

A&A

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In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) we present 120-168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44 • 30 and 1h00m +28 • 00 and spanning 4178 and 1457 square degrees respectively. The images were derived from 3,451 hrs (7.6 PB) of LOFAR High Band Antenna data which were corrected for the direction-independent instrumental properties as well as direction-dependent ionospheric distortions during extensive, but fully automated, data processing. A catalogue of 4,396,228 radio sources is derived from our total intensity (Stokes I) maps, where the majority of these have never been detected at radio wavelengths before. At 6 resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 µJy/beam; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2 ; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy/beam. By creating three 16 MHz bandwidth images across the band we are able to measure the in-band spectral index of many sources, albeit with an error on the derived spectral index of > ±0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20 resolution 120-168 MHz continuum images have a median rms sensitivity of 95 µJy/beam, and we estimate a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation (Stokes Q and Stokes U) image cubes consist of 480 × 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy/beam at 4 and 2.2 mJy/beam at 20 ; we estimate the Stokes I to Stokes Q/U leakage to be approximately 0.2%. Here we characterise and publicly release our Stokes I, Q, U and V images in addition to the calibrated uv-data to facilitate the thorough scientific exploitation of this unique dataset.

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Section: Value-added Cataloguementioning

confidence: 99%

The LOFAR Two-metre Sky Survey

Shimwell

Hardcastle

Tasse

et al. 2022

A&A

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250

108

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“…Moreover, the AGN and Galaxy Evolution Survey (AGES) has provided redshifts for 23,745 sources, including both normal galaxies and AGN, across 7.7 deg 2 of the field (Kochanek et al 2012). As one of the LoTSS Deep Fields, high-quality photometric redshifts have been determined for over 2 million optical sources (Duncan et al 2021). The Boötes field has been widely surveyed at radio wavelengths -with the WSRT at 1.4 GHz (de Vries et al 2002) and the VLA at 1.4 GHz (Higdon et al 2005) and 325 MHz (Croft et al 2008;Coppejans et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The LOFAR LBA Sky Survey: Deep Fields

Williams

Gasperin

Hardcastle

et al. 2021

A&A

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We present the first sub-mJy (≈ 0.7 mJy beam −1 ) survey to be completed below 100 MHz, which is over an order of magnitude deeper than previously achieved for widefield imaging of any field at these low frequencies. The high-resolution (15 × 15 arcsec) image of the Boötes field at 34-75 MHz is made from 56 hours of observation with the LOw Frequency ARray (LOFAR) Low Band Antenna (LBA) system. The observations and data reduction, including direction-dependent calibration, are described here. We present a radio source catalogue containing 1, 948 sources detected over an area of 23.6 deg 2 , with a peak flux density threshold of 5σ . Using existing datasets, we characterise the astrometric and flux density uncertainties, finding a positional uncertainty of ∼ 1.2 arcsec and a flux density scale uncertainty of about 5 per cent. Using the available deep 144-MHz data, we identified 144-MHz counterparts to all the 54-MHz sources, and produced a matched catalogue within the deep optical coverage area containing 829 sources. We calculate the Euclidean-normalised differential source counts and investigate the low-frequency radio source spectral indices between 54 and 144 MHz. Both show a general flattening in the radio spectral indices for lower flux density sources, from ∼ −0.75 at 144-MHz flux densities between 100 and 1000 mJy to ∼ −0.5 at 144-MHz flux densities between 5 and 10 mJy. Such flattening is attributable to a growing population of star forming galaxies and compact core-dominated AGN.

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“…In total, data for 16 bands were collected (cf. Table B.3 of Duncan et al 2021), although only 41% of our sources were imaged in all bands.…”

Section: Datamentioning

confidence: 99%

“…The redshift dependence is controversial, however. Other works did not find significant evidence for the evolution of the L radio /SFR ratio (Ibar et al 2008;Garn et al 2009;Mao et al 2011;Bourne et al 2011;Smith et al 2014;Duncan et al 2021;Smith et al 2021). Sargent et al (2010a,b) pointed out selection biases that may yield apparent evolution (see also Smith et al 2021).…”

Section: Introductionmentioning

confidence: 95%

“…The process is extensively described by Kondapally et al (2021), paper III of this series. This allowed us to derive high-quality photometric redshifts for around 5 million objects across the three fields (see Duncan et al 2021, paper IV of this series, for more details). Finally SED fitting techniques were exploited to provide accurate luminosities, SFRs and stellar masses of the radio-detected galaxies (Best et al 2021, paper V).…”

Section: Introductionmentioning

confidence: 99%

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The LOFAR Two-metre Sky Survey Deep fields: A new analysis of low-frequency radio luminosity as a star-formation tracer in the Lockman Hole region

Bonato,

Prandoni,

De Zotti

et al. 2021

Preprint

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We have exploited LOFAR deep observations of the Lockman Hole field at 150 MHz to investigate the relation between the radio luminosity of star-forming galaxies (SFGs) and their star formation rates (SFRs), as well as its dependence on stellar mass and redshift. The adopted source classification, SFRs and stellar masses are consensus estimates based on a combination of four different SED fitting methods. We note a flattening of radio spectra of a substantial minority of sources below ∼ 1.4 GHz. Such sources have thus a lower "radio-loudness" level at 150 MHz than expected from extrapolations from 1.4 GHz using the average spectral index. We found a weak trend towards a lower SFR/L 150 MHz ratio for higher stellar mass, M . We argue that such a trend may account for most of the apparent redshift evolution of the L 150 MHz /SFR ratio, in line with previous work. Our data indicate a weaker evolution than found by some previous analyses. We also find a weaker evolution with redshift of the specific star formation rate than found by several (but not all) previous studies. Our radio selection provides a view of the distribution of galaxies in the SFR-M plane complementary to that of optical/near-IR selection. It suggests a higher uniformity of the star formation history of galaxies than implied by some analyses of optical/near-IR data. We have derived luminosity functions at 150 MHz of both SFGs and radio-quiet (RQ) AGN at various redshifts. Our results are in very good agreement with the T-RECS simulations and with literature estimates. We also present explicit estimates of SFR functions of SFGs and RQ AGN at several redshifts derived from our radio survey data.

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The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

Cited by 67 publications

References 98 publications

The LOFAR Two-metre Sky Survey

The LOFAR Two-metre Sky Survey

The LOFAR LBA Sky Survey: Deep Fields

The LOFAR Two-metre Sky Survey Deep fields: A new analysis of low-frequency radio luminosity as a star-formation tracer in the Lockman Hole region

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